Working with trees delivers ASE results for Allan Brothers

2024-02-28 | Written by Alison Barber | Australian Fruitgrower article

Washington State grower Allan Brothers moved away from heavy reliance on plant growth regulators and toward Artificial Spur Extinction (ASE) to make crop-load management more precise. The business, which grows about 500 hectares of apples in the Yakima Valley, began using ASE in 2018 after finding chemical thinning responses too variable.

R&D manager Suzanne Bishop explains that ASE uses branch size to set a target fruit number and removes surplus floral spurs before bud break. In a third-leaf Scilate (Envy™) trial, a difference of only one to two fruit per branch was enough to change fruit size and colour, illustrating how sensitive quality can be to crop load.

The method uses branch cross-sectional area and a crop coefficient to calculate a target number of apples. Precision pruning also improves light distribution and fruit uniformity, and Allan Brothers reports that reducing excessive spur and leaf density has helped move more fruit into the retail “sweet spot” for size and colour.

The broader objective is not to eliminate every PGR use, but to understand tree physiology well enough that PGRs support rather than force the tree. Better record-keeping, earlier crop-load decisions and simpler downstream thinning are part of the same precision-management approach.